# Copyright 2022 Huawei Technologies Co., Ltd
# 
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import tensorflow as tf


def ssim(a, b, max_val):
    """Calculate SSIM of two images.

    Args:
        a: tensor, 4D image tensor.
        b: tensor, has the same shape with a.
        max_val: scalar, the max value of tensor a and b.
    """
    return tf.image.ssim(a, b, max_val, filter_size=11,
                         filter_sigma=1.5, k1=0.01, k2=0.03)


def ssim_multiscale(a, b, max_val):
    """Calculate multi-scale SSIM of two images.

    Args:
        a: tensor, 4D image tensor.
        b: tensor, has the same shape with a.
        max_val: scalar, the max value of tensor a and b.
    """
    return tf.image.ssim_multiscale(
        a, b, max_val, filter_size=11,
        filter_sigma=1.5, k1=0.01, k2=0.03
    )


def psnr(a, b, max_val):
    """Calculate PSNR of two images.

    Args:
        a: tensor, 4D image tensor.
        b: tensor, has the same shape with a.
        max_val: scalar, the max value of tensor a and b.
    """
    return tf.image.psnr(a, b, max_val)


